Results of studies during the past year utilizing a newly developed tumor induction technique in the hairless mouse have revealed certain extremely important data which include the induction of spindle-celled squamous cell carcinomas that histopathologically most closely resemble a Grade 4, highly malignant, metastazing form of squamous cell carcinoma usually seen primarily in areas of radio-dermatitis in human patients. Current studies are underway to differentiate the induction and progression of these tumors from the routinely induced Grade 2 to 3 type tumors during the applicaton of this technique. Concurrent studies will include prophylaxis and treatment of both types of tumors. Developments are underway to develop a sunscreening formulation that will prevent the photoaugmentation effect of UVA and UVB irradiated skin. This will require the formulation of substantiative chemicals that meet all of the criteria as outlined in te Federal Register on Sunscreens of 1978. Results of studies to be conducted during the ensuing year will provide further insight into the induction of squamous cell cancer and the proper development of prophylactic agents and treatment measures.